Zirconium oxide silica composite and method of making same



meme Feb. 22, 1927.

UNITED' STATES .GHARLES KINZIE, O1! NIAGABA I'M,

Annoy murncrunme comm,

1T0 Drawing.

My invention relates the derivation ofutilized for the preparation of zirconium composite pigments which mercial importance.

The objects of my invention are, among other things, the production of an improved zirconium oxide silicon oxide composite with novel and simplified methods of makhave great coming same after the zircon or baddeleyite has been converted into an acid zirconiumsolution with the separation of the zirconium as a double zirconium salt of an alkali metal. Such composite product may be successfully used as a suitable white opaquing agent for vitreous enamels in which it pos-v sesses great opaquing strength when compared with zirconium silicate even when milled to an extreme degree of fineness.

In the course of my investigations and experiments I have discovered a new and exceedingly economical method of preparing this novel zirconium oxide silicon oxide complex which, though varying little from natural zirconium silicate in chemi'cal proportions of Zr SiO yet diflers from zirconium silicate in that both the zirconium and silicon compounds are to a large extent co-precipitated from the acid solution containingboth in solution, and because of their intimate physical association in a chemically uncombined state the product possesses the full value of its zirconium oxide in the form of great opaquing strength but my tests have demonstrated that such product is the equivalent of the best ure zirconium oxide when considered oun for pound of ZrO content in terms 0 opaquing strength. In fact this zirconium oxide silicon oxide complex which I have produced is greatly superior to the most finely milled and purest white'zirconium silicate as an opaquing' pigment both in opaquing power and in purewhiteness of the enamels in which it is incorporated.

My tests have further shown that this composite product is not zirconium silicate but a very intimate association of zirconium oxide and silicon oxide in a chemicall PATENT FOFFI-CE,

NEW YORK, ASSIGNOB T0 OF NEW YORK, N. Y., A CORPORATION OF zmconnnr oxmn SILICA comrosrrn AND. METHOD or MAKING Application filed November 6, 1925. Serial re-67,435.

combined state;-'its chemical reactions are distinctively diflferent when com ared with the finest milled zircon (ZrSi It is well known that zircon is not materially af-' fected. by prolonged treatment with hot concentrated sulphuric acid, whereas my composite product reacts with-the zirconium oxide dissolving leaving the silica insoluble.

Againzircon is not materially affected bytreatment'with a dilute sulphuric acid and hydrofluoric acid mixture, whereas my composite product reacts losing'the silica as silicon tetrafluorid.

According to my invention the zirconium ore or mineral, for example zircon, is first decomposed by mixing same in-a finely milled state with a less, or not to exceed an lequal, quantity of alkali,.sodium carbonate em yiel ing a charge which when heated from 850 C. to 950 (1., preferably about 900 C. forms a mass that does not shrink materially and retains to a large extent its dry charac-' ter. without producing even a semi-pasty mass which is difiere'nt from those high temperature fusion methods in which the zirconium material is melted with molten alkalis. This decomposition wlll result in the formation of a zirconium residue readily preferred because. of its cheapness,

dissolving in dilute acids (preferably Sulphuric) with the silicon carried into the acid solution along with the zirconium. My ex-' periments have demonstrated that such fritted or roasted mass,- when disintegrated and leached with water and afterwards mixed with dilute sulphuric acid (20%), will usually show 97% ecomposition of the zircon in the ore used where equal weights of zircon and sodium carbonate were mixed and roasted. Such improved -methods of decomposing zirconium ores and minerals form the subject matterflof my pending application for patent filed in the U. 8. Patent- The following'example will disclose to others how my novel and improved compos'ite-product is advantageous y prepared.

Oflice October. 2?, 1925, Serial No.

When the raw material is zirconium s1l1- cate (zircon), it ispreferable first to treat same by the nitro cake fusion process as set forth in the-U; S. Barton and Kinzie Patent No. 1,451,004 of April 10, 1 m, to remove therewith entangled impurities, "such-as rg which case some of the titanium oxide can be left in or even introduced into the batch prior to practising my improved methods. Where baddeleylte is used which contams both free zirconium 0." le as well as z1r-.

conium silicate, it is sometimes referable first to extract by hydrochloric acid the several per cent of iron oxide contained before proceeding with the process proper or this acid extraction of iron may be left to the last as in this process the iron oxide appar ently does not become so closely entangled with the major constituents as not to..be easily removed.

The ore is finely milled to a point where nearly all will pass through a 325 mesh sieve; wet milling is preferable to dry millmg.

Sodium carbonate is incorporated with the milled ore in amount equivalent pound for ound of ore used and the charge-is drie or such milled ore may be separately dried and dry sodium carbonate is mixed with dried ore.

The mixture of equal weights of zirco- -nium ore and sodium carbonate is now several hours at a. temperature of about 900 C., or until tests show that the zirconium silica combination as in ZlI'COIl has been to all practical purposes completely broken up. This roasting treatment apparently results in the formation of: sodium zirconate and sodium silicate of a basic nature.

The roasted product is then reduced to a fine state of sub-division, preferably and most conveniently by wet milling in pebble mill with water and-discharged. In some cases the slurry can be treated directly with acid, but due to the fact that most zircon minerals contain small amounts of discoloring impurities which are rendered soluble in water by this alkali roasting process, I prefer first to dilute with water and then let the product settle giving the batch several washes by settling decantation, or it desired 'by direct filtration.

The water insoluble fraction when dried at 110 C. has substantially the following chemical composition At any rate the washed residue is finally obtained in the form of a. slurry; and before adding some sodium chloride or other sodium or like salt it is treated with sulphuric acid made up preferably of 1 volume of H 50, and 1 volume of water. The amount of acid is approximately suflicient to form Na SO, with Na O content of sludge, normal zirconium sulphate with the total zirconium fraction of sludge, assuming that the amount of free dilute H SO, insoluble zirconium oxide present is later altered and recombined in more desirable form. The manner or order of addition of these materials one to the other is immaterial, so long as conditions are such that the acid is given an opportunity to dissolve out the soluble zirconium fraction as well as the silicon which is nearly all dissolved. I

prefer to adjust the concentration of the solids suspended in water and the acid strength and temperature so that ample time elapses before the mass solidifies; for instance, if the acid were too strong or too hot, or the zirconium silica residue contained too little" water, the mass would solidify before the desired solution would have opportunity to be accomplished. I also aim to allow sufficient time to transfer the mass from the mixing vessel to ,a suitable vessel for solidification to avoid having the mass solidify in a container having an agitator.

The solution containing the fraction of zirconium oxide insoluble in this concentration of acid is then transferred from the mixing vessel into a suitable oven vessel, preferably a vat with slopin sides, and allowed to solidify. This setting up may be hastened by external application of heat. When the charge has set it assumes the nature of a semi-transparent jelly,'which/ can be removed in lumps or in mass and then can be dried. Upon drying the appearance of mass changes to a crystalline structure and does not shrink materially; it alsoloses its transparent appearance and becomes a white, opaque, pulvcrulent material which I then treat as follows The mass is charged into a suitable furnace capable of heating to a point where the crystalline and other sulphates are decomposed. During the course of this heat application the sodium chloride, if such is added as indicated, is decomposed and forms Na,S() the zirconium salt decomposes forming zirconium oxide, the sodium in combinations of zirconium and silicon is recombined forming ultimately sodium sulphate,

and the siliconcompound upon such hcating is altered to silicon dioxide. It is assumed that at the initial stage of heating the insoluble zirconium oxide residue is first altered to form either zirconium sulphate or moreprobably sodium zirconium sulphate; probably all the zirconium crystallizes out in the early stages as sodium zir conium sulphate and if the silicon complexes pend somewhat upon theamount'of sodium chloride added and the amount-of sodium sulphate present. I prefer to keep the amount of sodium sulphate in the ultimate.

1 heated mass below the point where the melted salt would form a fused mass. Under preferred conditions of this process the mass as discharged from the furnace is in the form of dry, only slightly sintered, aggregates. However, suflicient sodium chloride could be addedia form Na SO and HCL by combination with allthe sulphuric acid as formed, and in this case the charge would more nearl approach a fusion. However I do not pre er this and will ordinarily prefer to work with a-dr charge-which may then be handled in ry state... Whetherthe charge is dry during heating operation or whether it is in state of semtfusion, or even in a liquid. mas does not in the least afi'ect the result.

Duringthe heating of this sulphate mass it is desirable to maintain an oxidizing atmosphere because if the atmosphere is allowed to become of a reducing nature, the

sodium sulphate would be reduced to sodium sulphide; such alkaline material would in turn begin to combine with silica and zirconium which should be avoided because the efiect is a discoloration of product and combinations of alkali with the zirconium and silicon should be prevented.

The product as discharged from the furnace is then disintegrated with an ample supply ofwater, preferably by using a. pebble mill to break down the'aggregates to a -very .fine state. This requires but a few hours milling when the charge is diluted with water. and by any suitable means, preferably settling-and .decantation, the soluble sodium sulphate is thoroughly extracted leaving a zirconium oxide silicon oxide complex of great opaquing strength and great whiteness, provided the zirconium ore .was

. relatively'pure as the starting material.

When baddeleyite or certain other zir--.

coniumores are. used, it is preferable,- before completely washing out the sodium sulphate, to digest the charge with a dilute hot mineral acid to remove the soluble iron. Such process leaves the iron compounds in such. a state as to be readily soluble in hydrochloric acid for instance.

However if the raw material is a chemi-'.

. have taken place.

cally refined zircon silicate mineral no acid extraction is required at the' finish since the product will be found to be of a pure white color.

As a practical illustration of the procedure to be followed in working out my improved methods, 100 parts by weight of finely-milled zircon and 100 parts by we ght of sodium carbonate are mixed and heated' for about three hours at about 900 C. The mass is then cooled and milled with about 400 parts of water for several hours, or until the aggregates are reduced to fine state. The charge is removed from the mill and washed (notexcessively) with cold water to remove the dissolved chromium, manganese, etc. This water washing may be omitted if the mineral used is sufiiciently free of impurities. 7

To the slurry volume of about 300 c. c.

containing the sodium zirconate, sodium silicate and'zirconium oxide is added about 60 grams of sodium chloride which is stirred in and allowed to dissolve; thereafter is added to the charge from 160 to 210 parts of H SO in form of a dilute solution conlowed to cool it will set; but I prefer to heat and stir while heating. Upon heating a minute or so the charge will solidify into stiff mass that may be easily handled. I prefer to dry this and thenheat at temperature from say 900 to 1050 C. for period of say three hours or until the reactions The mass is removed from furnace. disintegrated with ample water, washed well to free it from sodium sulphate, and finally dried.

The composition of a typical complex product from baddeleyite is as follows Percent. sio mr 17.06 zro r 82.80 Nail); Y. 0.16

The composition of a product made from chemically refined zirconium silicate is as follows i Per cent. Si0 28.94 I'O 7 V 70.80 Na om p self to treatment of a variety of zirconium ores and to the alteration and reformation of zirconium and silicon contents thereof into more powerfully opaque and less highly colored roducts,

The a vantages of my improved methods of reparing such composites reside largely in ringing both the zirconium and silicon into solution and then through heat to cause a co-precipitation of at least ,a part of the silicon compounds as a gelatinous mass mate physical association.

Other acids than sulphuric acid may be used as an addition to the charge, for example, hydrochloric or nitric or oxalic acids,

which are effective solvents for the zirconi-' um and silicon in the roasted mass. In case hydrochloric or nitric acid was employed, I would add a sulphate, such as sodium sulphate, potassium sulphate, or the equiva lent in the form of a mixture of sodium chloride or potassium chloride and sulphuric acid which upon heating would cause the zirconium to separate as a double potassium zirconium sulphate or a mixture of the two.

Sodium chloride is preferably used in my process on account of its cheapness and also because it forms sodium sulphate and hydrochloric acid which is more readily expelled from the charge than sulphuric acid.

I claim as my invention:

1. The method of preparing a zirconium oxide silica composite which comprises heating zirconium-containing material with a less quantity of an alkali to substantial decom osition of said material, treating the resi us with acid to obtain both zirconium and silicon compounds in solution, then heating the char e in the presence of sufli cient alkali meta compound to precipitate the zirconium compound as a double zirconium salt of the alkali metal, and finally drying the resulting product.

2. The method of preparing a zirconium oxide silica composite which comprises heating zirconium-containing material with a less quantity of an alkali to substantial decom osition of said material, leaching the resu ting product with water, treating the residue with sulphuric acid to obtain both zirconium and silicon compounds in soluing the charge in the presence of sufficient sodium chloride to precipitate the zirconium compound as a double sodium zirconium salt, and finallydrying the resulting product.

4. The method of preparing a zirconium oxide silica composite which comprises heat ing zirconium-containing material with a less quantity of an alkali to substantial de' composition of said material, leaching the resulting product with water, treating the residue with sulphuric acid to obtain both zirconium and silicon compounds in solu tion, then heating the charge in the presence of sufficient sodium chloride to re'cipitate the zirconium com ound as a dou 1e sodium I zirconium salt, an finally drying the resulting product.

5. The method of preparing a zirconium oxide silica composite which comprises heating zirconium-containing material with a less quantity of an alkali to substantial decomposition of said material, leaching the resulting product with water, treating the.

residue with acid to obtain both zirconium and silicon compounds in solution, then heating the charge in the-presence of sufficient alkali metal compound to precipitate.

the zirconium compound as a double zirconium salt of the alkali metal, calcining the charge to completion of the reactions therein, and leaching the soluble substances from the insoluble chemically uncombined zirconium oxide silica composite.

6. The method of preparlng a zirconium oxide silica composite which comprises heat-- ing zirconium-containing material with a less quantity of an alkali to substantial decomposition of said material, leach ng the resulting product with water, treat ng the residue with sulphuric acid to obtaln both zirconium and silicon compounds 1n solution, then heating thecharge in the presence of sufficient alkali metal compound to precipitate the zirconium compound as a double zirconium salt of the alkali metal, calcining the charge to completion of the reactions therein, and leaching the soluble substances from the insoluble chemically uncombmed zirconium oxide silica composite.

7. The method of preparing a zirconium oxide silica composite which comprises heating zirconium'containing material with a less quantity of an alkali to substantial de- 1 less quantity of an alkall to substantial decomposition of said material, leaching the resulting product with water, treating the residue with sulphuric acid to obtain both zirconium and silicon compounds in solution, then heating the charge in the pres- 'ence of sufiicient sodium chloride to precipitate the zirconium compound as a double sodium zirconium salt, calcining the charge to completion of the' reactions therein, and leaching the soluble substances from the insoluble chemically uncombined zirconiu oxide silica composite.

9. In the method of preparing a zirconium oxide silica composite from an acid soluble zirconium compound, the steps whichconsist in leaching same with water, then heating the residue with acid to obtain both zirconium and silicon in solution, and then.

heating the charge in the presence of sufficient neutral alkali metal compound to precipitate the zirconium compound as a double zirconium salt of the alkall metal,

10. In the method of preparing a zirconium oxide si ica composite from an acid soluble zirconium compound, the stepswhlch consist in treating said compound' w1th 'd1- lute sulphuric acid to obtain both zircomum and silicon in solution, and then heat ng the char e in the presence of suflicient neutral alkafi metal compound to precip tate the zirconium compound as a double zirconium salt of the alkali metal. I

11. In the method of preparing a z1 rconium oxide silica composite from an acid soluble zirconium compound, the steps whlch consist in leaching same with water, then treating the residue with dilute sulphuric acid to obtain both zirconium and silicon in solution, and then heating the charge in the presence of sodium chloride to precipitate the zirconium compound as a double sodium zirconium salt. v 12. In the method of preparing a zirconium oxide silica composite from z ir-- conium-containing material, the steps which comprise heatingthe material mixed witha less quantity of an alkalito substantial decomposition of said material without shrinkothe due soluble in dilute acids, leaching same with water and treating the residue with acid to obtain both zirconium and silicon in solution, then heating the charge in the presence of suflicient neutral alkali metal compound to precipitate the zirconium compound as a double zirconium salt of the alkali metal, and finally drying the resulting product.

13. In the method of preparing a zirconiu'm oxide silica composite from zirconiumcontaining material, the steps which com-v prise heating the'material mixed with a less quantity of an alkali to 'substantialdecomposition of said material without shrinking the mass and forming a zirconium residue soluble in dilute acids, leaching same with water and treating the residue with acid to obtain both zirconium and silicon in solution, then heating the charge in the presence of sufiicient neutral alkali metal compound to precipitate the zirconium compound as a double zirconium salt of the alali metal, calcining the charge to completion of reactions therein, and leaching the soluble substances from the insoluble chemically uncombined zirconium oxide silica composite.

14. characterized as being an opaque powder essentially white in color and soluble in sulphuric acid leaving the silica insoluble and as consisting, by analysis, preponderatingly of minute, crystalline zirconium oxide and also containing silica in quantity less than said zirconium oxide, said compounds being intimately physically associated, though chemically uncombined, with each other.

' 15. A zirconium oxide silica com osite characterized as being an opaque pow er essentially white in color and soluble in sulphuric acid leavin the silica insoluble and as A zirconium oxide silica compositeconsisting, by analysis, of not less than fifty less than said zirconium-oxide, said compounds being intimately physically associated, though chemically uncombined, with each other.

16. A zirconium oxide silica composite characterized as being an opaque powder essentially white in color and soluble in sulphuric acid-leaving the silica insoluble and as consisting, by analysis, of not less than fifty percent of minute, crystalline zirconium oxide and also containing silica in quantity less than said zirconium oxide, and less than one percent of sodiumoxide, said compounds being though chemically uncombined, ;with each '17. A zirconium oxide silica composite characterized as being a calcined product, in

intimately physically associated,

form an opa ue powder essentially White in color, and so uble in sul huric acid leaving the silica insoluble, and as consisting, by analysis, preponderatingly of minute, crystalline zirconium oxide and also containing silica in quantity less than said zirconium oxide, said compounds being intimately physically associated, though chemically uncombined, with each other.

18. As a new composition of matter, a calcined product being an intimatel physicall associated, but chemically uncoml ined, prod uct composed of minute crystalline zirconium oxide and silica varying in Zl'O to $10 ratio, viz: (Z1'O "1.80 to SiO -1) to (ZrO 7 to SiO 1) and in form an opaque crystalline pow er, essentially white in color, and also soluble in sulphuric acid leaving the silica in amorphous form and insoluble.

19. In the method of preparing a zirconium oxide silica composite from an acid soluble zirconium compound, the steps which consist in leaching same with water, then treating the residue with acid to obtain both zirconium and silicon in solution, and then heating the charge in the presence of suflicient neutral alkali metal compound to precipitate the zirconium compound as a double zirconium salt, calcining the charge to completion of reactions therein, and leaching the soluble substances from the insoluble chemically uncombined zirconium oxide silica composite. i

CHARLES J. KINZIE. 

